RU2368694C1 - Rail steel - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: steel contains carbon, silicon, manganese, chrome, molybdenum, vanadium, niobium, boron, nickel, aluminium, nitrogen, calcium, iron and admixtures, at following correlation of components, wt %: carbon 0.85-1.30, silicon 0.10-1.20, manganese 0.20-1.60, chrome 0.10-1.10, molybdenum 0.001-0.30, vanadium 0.03-0.15, niobium 0.0001-0.005, boron 0.0003-0.002, nickel 0.05-0.30, aluminium not more than 0.005, nitrogen 0.007-0.02, calcium 0.0005-0.005, iron and admixtures are the rest. In the capacity of admixtures steel contains sulfur not more than 0.015 wt %, phosphor not more than 0.020 wt % and copper is not more than 0.20 wt %.

EFFECT: it is increase complex of physical-mechanical properties, wear resistance and impressive durability of rails.

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Description

The invention relates to ferrous metallurgy, in particular to the production of steel for railway rails with an improved set of properties, including increased wear resistance and contact fatigue strength.

Known steel [1], containing (wt.%): 0.6-1.20 C; 0.1-1.2 Si; 0.4-1.4 Mn; 0.005-0.030 N; 0.005-0.050 Al; 015-0.070 Mo; 0.1-1.0 Cr; 0.005-0.070 V; 0.01-1.50 Ni; 0.004-0.050 Nb; 0.01-1.50 Cu; 0.0001-0.0100 Ti; 0.002-0.050 S; 0.0001-0.0050 B; 0.0005-0.020 Mg; Fe - ost.

Significant disadvantages of this steel are the low toughness and contact fatigue strength of the rails, due to the high aluminum content in the steel, which leads to contamination of its coarse line inclusions of alumina.

Also known rail steel [2], containing (wt.%): 0.83-0.95; 0.3-0.7 Si; 0.6-1.1 Mn; 0.08-0.15 V; not more than 0.005 Al; 0.012-0.020 N; 0.0005-0.005 Ca; 0.05-0.5 Cr; 0.11-0.3 Mo; 0.05-0.3 Ni; 0.0005-0.005 Zr; 0.0005-0.005 REM; not more than 0.015 S; 0.020 P; 0.020 s; Fe - ost.

The main disadvantage of steel is the insufficient wear resistance of rails, due to the relatively low content of carbon, manganese, silicon, chromium and molybdenum.

Known selected as a prototype rail steel [3], containing (wt.%): 0,85-1,20 C; 0.10-1.00 Si; 0.20-1.50 Mn; 0.50-1.00 Cr or 0.85-1.20 C; 0.40-1.00 Si; 0.20-0.40 Mn; 0.35-0.50 Cr, and the sum of the indicators of the content of Si / 4 + Mn / 2 + Cr is 0.8-1.8%; as well as one or at least two elements selected from the group comprising Mo, V, Nb and B, impurities and Fe — stop.

A significant disadvantage of this steel is an increased tendency to brittle fracture and reduced operational durability.

The desired technical result of the invention is to increase the complex of physico-mechanical properties, wear resistance and contact fatigue strength of rails.

To achieve this, steel containing carbon, silicon, manganese, chromium, molybdenum, vanadium, niobium, boron and iron is characterized in that it additionally contains nickel, aluminum, nitrogen, calcium in the following ratio of components (wt.%):

carbon 0.85-1.30 silicon 0.10-1.20 manganese 0.20-1.60 chromium 0.10-1.10 molybdenum 0.001-0.30 vanadium 0.03-0.15 niobium 0.0001-0.005 boron 0.0003-0.002 nickel 0.05-0.30 aluminum no more than 0.005 nitrogen 0.007-0.02 calcium 0.0005-0.005 iron and impurities rest,

the amount of impurities is limited in the following ratio (wt.%):

sulfur no more than 0.015 phosphorus no more than 0,020 copper no more than 0.20

The inventive chemical composition of the steel is selected based on the following premises.

The selected carbon content provides an increase in yield strength, temporary tensile strength, hardness and wear resistance of rail steel. The transition to hypereutectoid steels leads to a decrease in austenite grain growth compared to hypereutectoid steels.

With a carbon content of more than 1.3%, the fragility of rails increases significantly.

The increase in the content of Si, Mn, Cr compared with the prototype is also associated with the need to increase the wear resistance of hypereutectoid steel with a working contact wheel-rail.

An increase in silicon content to 1.20% is associated with the need to increase the deoxidation of steel with a decrease in the aluminum content in it, which ensures an increase in the purity of steel by inclusions of plastic silicates, which reduce the toughness.

An increase in the concentration of manganese to 1.60% increases the hardenability of steel, reduces the critical cooling rate.

Molybdenum within the specified limits provides a dispersed hardened structure, increases the strength properties, hardness, toughness and wear resistance. The introduction of molybdenum enhances the action of aluminum, a decrease in the content of which will not lead to a decrease in resistance to brittle fracture.

In general, the selected ratio of Mn, Si, Cr, Mo, B in steel containing 0.85-1.30% C provides a decrease in the austenite transformation temperature and a more dispersed troostite structure in comparison with quenching sorbitol.

The introduction of Nickel in the claimed range provides an increase in ductility and toughness of steel. Its content up to 0.05% does not have a positive effect on the properties of steel, and at a concentration of more than 0.3% this characteristic does not exceed the determined values.

The joint introduction of V, Nb, N into steel leads to an increase in strength properties and resistance to brittle fracture due to the formation of dispersed particles of vanadium and niobium carbonitrides. When the concentration of vanadium is less than 0.03%, niobium is less than 0.0001%, nitrogen is less than 0.007%, an increase in the endurance of steel is not provided. With an increase in the content of vanadium, niobium and nitrogen in steel more than the declared limits, the amount of carbonitrides in it increases, providing an undesirable increase in strength properties. With an increase in nitrogen of more than 0.02%, cases of spotted segregation and "nitrogen boiling" (bubbles in steel) are possible.

Reducing the aluminum content to 0.005% and modifying the steel with calcium from 0.0005 to 0.005% ensure the production of high-purity metal from inclusions of aluminates, lead to the formation of globular non-metallic inclusions, to a decrease in their size and quantity. However, the introduction of calcium of more than 0.005% leads to contamination of its large globules and increases the cost of steel production. Calcium at a concentration of less than 0.0005% practically does not affect the modification of inclusions.

The limitation of the content of copper, sulfur, and phosphorus was chosen in order to improve the quality of the surface and increase the ductility and toughness of steel. In addition, the concentration of sulfur determines the red brittleness, phosphorus-cold brittleness of steel.

The inventive chemical composition of rail steel provides rails with increased contact fatigue strength and wear resistance when cooled by compressed air.

A series of experimental swimming trunks was smelted in DSP-100I7 arc furnaces. The chemical composition is shown in table 1. The metal was cast on a continuous casting machine. The resulting billets were heated and rolled according to conventional technology onto rails of the P65 type, which were subjected to differentiated hardening with compressed air. The data presented in table 2 show that the mechanical properties and hardness of the rails of the inventive steel are significantly higher than the rails of steel E83F [4]. An increase in the hardness and strength properties of rails increases the increase in their wear resistance and contact fatigue strength.

List of sources taken into account

1. Patent JP 2004-076112 A, IPC C22C 38/00; 38/06; 38 / 5-1, 2004

2. Patent RU 2259416 C2, IPC C22C 38/24, 38/28; 38/46; 38/50, 2005

3. Patent RU 2139946 C1, IPC C21C C 21D 9/04; C22C 38/04, 1996

4. TU 0921-125-2001 "Railway rails of increased wear resistance and contact endurance."

Table 1 The chemical composition of steel Structure Mass fraction of elements,% FROM Mn Si V Al N Sa Nb Cr Mo Ni one 0.85 1.20 1.10 0,03 0.005 0.012 0,0005 0,0005 0.60 0.005 0,0005 2 0.87 0.30 1.20 0.09 0.005 0.014 0,0008 0,0008 0.10 0.001 0.005 3 0.85 0.85 0.30 0.12 0.004 0.017 0.0020 0.0015 1.10 0.15 0,0007 four 0.88 1.00 0.60 0.14 0.005 0.015 0.0010 0.0016 0.80 0.20 0.0001 5 0.94 0.95 0.50 0.11 0.005 0,020 0.0030 0.003 0.30 0.26 0.004 6 0.95 1.10 0.69 0.15 0.005 0.018 0.0049 0.005 0.50 0.30 0.001 7 1.00 0.61 0.30 0.08 0.005 0.007 0,0006 0,0005 0.70 0.12 0.004 8 1.20 0.75 0.45 0.11 0.003 0.010 0.0015 0,0007 0.90 0.19 0.005 9 1.25 0.96 0.61 0.13 0.002 0.018 0.0034 0.003 0.50 0.20 0,0006 10 1.30 1.09 0.70 0.15 0.005 0.009 0.0051 0.005 1.00 0.30 0.001 TU-0921-125-2001 Steel E83F 0.78-0.88 0.75-1.05 0.25-0.45 0.03-0.15 no more than 0,02 - - - ≤0.15 - ≤0.15

table 2 Mechanical properties of differentially hardened rails Option σ _t σ _in δ ₅ ψ Hardness N / mm ² % HB ₁₀ HB ₂₂ HBPC one 1030 1413 12 25 401 388 415 2 990 1352 12 33 388 363 388 3 990 1363 12 33 388 388 388 four 1029 1391 eleven 32 388 375 388 5 1039 1372 10 31 388 388 401 6 1049 1412 10 31 388 388 415 7 1060 1423 12 24 415 401 430 8 1080 1443 eleven 23 415 415 430 9 1090 1452 10 22 415 415 430 10 1090 1462 9 twenty 410 415 440 TU-0921-125-2001 Steel E83F 880 1274 7 26 ≥352 ≥341 ≥363 Note: NVpgk - hardness on the rolling surface of the rail head; HB ₁₀ , HB ₂₂ - hardness at a distance of 10 and 22 mm, respectively.

Claims (1)

Rail steel containing carbon, silicon, manganese, chromium, molybdenum, vanadium, niobium, boron, iron and impurities, characterized in that it additionally contains nickel, aluminum, nitrogen and calcium in the following ratio, wt.%:
carbon 0.85-1.30 silicon 0.10-1.20 manganese 0.20-1.60 chromium 0.10-1.10 molybdenum 0.001-0.30 vanadium 0.03-0.15 niobium 0.0001-0.005 boron 0.0003-0.002 nickel 0.05-0.30 aluminum no more than 0,005 nitrogen 0.007-0.02 calcium 0.0005-0.005 iron and impurities rest
the amount of impurities is limited in the following ratio, wt.%:
sulfur no more than 0.015 phosphorus no more than 0,020 copper no more than 0.20